I don't know why everyone doesn't use the same converter! I haven't looked into any of them in detail… As for what a TeX distribution is: it's all the stuff (be

I don't know why everyone doesn't use the same converter! I haven't looked into any of them in detail… As for what a TeX distribution is: it's all the stuff (beyond the source code of TeX itself, which is maintained solely by Knuth) needed to get TeX and related systems in a usable form. This includes the to-C converter and build scripts, for TeX and for other programs/extensions like pdfTeX, the major macro packages like LaTeX and “format files” for them, font information for commonly used fonts, lots of “packages” written by lots of people over the years, hyphenation rules for languages, other programs like makeindex etc., DVI viewers and converters, TeX editors — the entire ecosystem that a typical TeX user may want. (Some distributions more minimal than others… TeX Live and MiKTeX are probably the two main ones today.)